<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Flex 布局</title>
    <style>
        .body{
            margin : 0;
            height: 100vh;
            background-color: #eee;
        }
        *{
            border : 1px solid;
        }
        .flex{
            display: flex;
        }
        .baiSe{
            background-color: white;
        }
    </style>
</head>
<body class="flex">
    <!-- 侧边栏 -->
    <div style="width: 200px;" class="baiSe">

    </div>
    <!-- 主区域 -->

</body>
</html>